Patient HM

8 Key excerpts on "Patient HM"

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  Forgetting

  Explaining Memory Failure

  • Michael W. Eysenck, David Groome, Michael W. Eysenck, David Groome, Author(Authors)
  • 2020(Publication Date)
  • SAGE Publications Ltd

    (Publisher)

  While the surgery was considered a success in terms of managing the seizure disorder, an unexpected consequence was a severe and irreversible memory loss characterised by severe and global anterograde memory impairment (i.e. profoundly disrupted ability to form new memories) and a temporally graded retrograde amnesia (i.e. loss of previously acquired memory, with greater deficit in the time period close to the surgery and better memory moving back in time). The subsequent neuropsychological and neuroanatomical descriptions of HM have provided significant insight into the organisation of human memory and its instantiation in the brain (see also Corkin et al., 1997; Corkin, 2002). From HM, and from other cases of amnesia, we have learned that damage to the hippocampus and related medial temporal lobe regions, whether by surgical resection, as in HM, or following anoxia or other neurological insult, results in a profound yet circumscribed amnesia. The specificity of the observed impairment in HM was of critical importance. The impairment was specific to the domain of memory, as well as specific within the domain of memory. The impairments are seen in aspects of memory function, disproportionate to any deficits in general cognitive or intellectual abilities. HM had not lost the capacity for speech and language (i.e. he did not have aphasia) and his other cognitive abilities were intact including attention, problem solving, and reasoning. Moreover, the observed impairment in HM affected only certain aspects, or forms of memory

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  Cases of Amnesia

  Contributions to Understanding Memory and the Brain

  • Sarah E. MacPherson, Sergio Della Sala, Sarah E. MacPherson, Sergio Della Sala(Authors)
  • 2019(Publication Date)
  • Routledge

    (Publisher)

  2The Earthquake that Reshaped the Intellectual Landscape of Memory, Mind and Brain

  Case HM

  Donald G. MacKay

  Please give our readers some background information about case HM

  The currently ongoing revolution in the scientific understanding of memory, mind and brain began in 1953 with amnesic patient Henry Molaison, known widely only as HM until recently. To remedy life-threatening epilepsy at age 27, Henry underwent surgery that inadvertently destroyed brain structures in the medial temporal lobe, and he suffered catastrophic memory failures for the remaining 56 years of his life. He also experienced deficits in creating and expressing novel ideas, comprehending unfamiliar concepts and perceiving the unexpected in his visual world.

  If Henry never had his 1953 operation, would the scientific community know as much about memory, mind and brain as it does now?

  Case HM was a major earthquake that forever reshaped the intellectual landscape of memory, mind and brain. Scientific understanding of memory took off with this one case. Henry is the main reason we know that the hippocampal region is essential for forming new memories (see Figure 2.1 ). Case HM also helped the world understand what memories are and why the distinction between new versus old memories is so important.

  Did serendipity play a role in your research with Henry, or could you have foreseen every step in the process?

  Serendipity certainly contributed to my initial discoveries with Henry in 1966 (see MacKay, 1972). I was a 23-year-old graduate student at MIT. My mentor, Hans-Lucas Teuber (see Figure 2.2 ), introduced me to Henry and suggested that I test his language abilities using a sentence comprehension paradigm that I was developing at the time. It never crossed my mind that Henry’s performance in my experiment would alter the direction of my research over the next half century.

  Figure 2.1  The human hippocampus in the medial temporal lobe next to the midbrain. Henry Gray (1918) Anatomy of the Human Body

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  Memory

  The Key to Consciousness

  • Richard F. Thompson, Stephen A. Madigan(Authors)
  • 2013(Publication Date)
  • Princeton University Press

    (Publisher)

  The two patients did show some retrograde amnesia but it was relatively mild compared to the anterograde amnesia. Their abilities to recognize objects and their language skills were intact. AMNESIA 119 The memory problems of the epileptic Patient HM have been studied for 50 years now, and many other similar cases have been identified since the 1950s. The surgical procedure that HM expe- rienced was discontinued when the adverse side effects were dis- covered, but other cases of temporal lobe amnesiacs have occurred as a result of brain damage from accidents, encephalitis, or condi- tions that interrupt blood supply to the brain. Under some con- ditions, these kinds of events damage hippocampal tissue without much damage to other areas. The findings of these studies have had an enormous impact on memory theory. To start with, they drew attention to the pos- sible importance of the hippocampus for learning and memory. Figure 5-1 is a coronal (frontal cross-section) view of the hippo- campus in the left hemisphere of the brain. It is about eight centi- meters long and is located on the inner (folded) part of the temporal lobe in both brain hemispheres. (“Hippocampus” is Greek for “seahorse.” With a little imagination, you can see why this brain region is so named by looking at the structures in Figure 5-1.) A second major finding of temporal lobe amnesia research is that hippocampal damage impairs some kinds of learning and Hippocampus Dentate Gyrus Entorhinal Cortex Parahippocampal Cortex Perirhinal Cortex Hippocampus Subiculum FIGURE 5-1 The hippocampal complex in the temporal lobes of the hu- man brain. 120 MEMORY memory functions while leaving others unaffected. For example, HM’s memory has been described as consisting of the following sets of spared functions: • Intact immediate or short-term memory (his memory span is in the normal range). • Intact general mental functioning (his IQ did not decrease following the surgery).

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  Memories That Matter

  • Singer, Jefferson A.(Authors)
  • 1(Publication Date)
  • New Harbinger Publications

    (Publisher)

  Although the seizures subsided, H.M. displayed a remarkable change in memory that no one had anticipated. He suffered from two major forms of memory problems. First, although he could remember events from his life up to age sixteen, he could not remember any events between then and the age of twenty-seven, which was his age at the time of the surgery. More concerning, and what has led to H.M.’s enduring fame in memory research is that he also lost the capacity to create any new memories. In other words, he rapidly forgot any recent experiences that occurred in his life and consequently could no longer learn anything new. He would need to be introduced to his doctors every day. He could not accumulate any sense of the passage of time or events of history. He was stuck in a period in which Truman was president and World War II had recently ended. Each time he learned that his mother had died, he would again register the shock and pain of this news. 16 Memories That Matter He lived this way for over forty years and patiently endured, with reasonably good humor, literally hundreds of studies of his memory functioning. As a living laboratory, H.M. helped to teach researchers the critical importance of the hippocampus, the seahorse-shaped por- tion of the midbrain or temporal region that plays a crucial function in the conversion of new information into stored long-term memories. Besides teaching us about the linkages between portions of the brain and the different components of memory, H.M.’s tragic situation led many researchers to speculate about the relationship of memory to the self.

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  Memory

  Neuropsychological, Imaging and Psychopharmacological Perspectives

  • Gérard Emilien, Cécile Durlach, Elena Antoniadis, Martial Van der Linden, Jean-Marie Maloteaux(Authors)
  • 2004(Publication Date)
  • Routledge

    (Publisher)

  Studies on the role of the medial temporal lobe in the memory system suggest that this part of the brain performs a critical function beginning at the time of learning to establish a long-term declarative memory (Mishkin, 1982; Squire, 1987). Its role continues after learning for a lengthy period of reorganisation and consolidation whereby memories stored in neocortex eventually become independent of the medial temporal lobe memory system. This process, by which the burden of long-term permanent memory storage is gradually assumed by the neocortex, ensures that the medial temporal lobe system is always available for the acquisition of new information. Such a hypothesis suggests that lesions of the medial temporal lobe interfere only with the long-term storage of new memories. Patients like HM, who due to the severity of his epilepsy had the medial temporal lobes of his brain removed to prevent almost constant seizures, retain a reasonably good memory of earlier events (Milner, 1985; Scoville & Milner, 1957; Squire, 1987). He showed deficiency in declarative memory—he cannot recollect new events in his life or new facts about the world but is able to learn new visuomotor skills (e.g., reading in a mirror after several practice sessions) without awareness of having been previously tested. Patient HM’s case triggered several important hypotheses that have significantly impacted the study of the neuroanatomical basis of memory. HM’s deficits were initially attributed to his hippocampal damage (resulting from his bilateral medial temporal lobectomy). This was the first case implicating the hippocampus in memory. The view that mnemonic functions are diffusely represented throughout the forebrain was challenged. The findings from HM triggered many studies to investigate the role of the hippocampus in learning and memory in both animals and men. They provided the first evidence that implicit memory could survive in the absence of explicit memory. The implication of the medial temporal lobes in memory consolidation was suggested.

  The first lesions in most cases of AD may occur in the medial temporal lobe and this may account for amnesia being the most common initial problem in AD (Hyman et al., 1984). Unlike patients with pure amnesia, AD patients have a dementia defined by the compromise of at least one additional, non-mnemonic function. Further, AD patients also have early damage to cholinergic neurons in the basal forebrain and lesions in that area cause declarative memory impairments (Arendt et al., 1983). Therefore, it is not appropriate to ascribe the amnesia in AD exclusively to medial temporal injuries.

  Postmortem analysis of medial temporal damage in patients with well-characterised amnesias shows that damage restricted to a small part of the hippocampal region, the CA1 field, is sufficient to produce clinically significant anterograde amnesia. More extensive damage to additional medial temporal structures aggravates the severity of the anterograde amnesia and the temporal extent of the retrograde amnesia. When lesions extend beyond the hippocampal region into the entorrhinal and perirhinal cortices, retrograde amnesia extends back one or two decades (Corkin et al., 1997; Rempel-Clower et al., 1996).

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  Neurobiology of Language

  • Gregory Hickok, Steven L. Small(Authors)
  • 2015(Publication Date)
  • Academic Press

    (Publisher)

  Squire, Stark, & Clark, 2004 ).

  After his surgery, H.M. suffered from both anterograde and retrograde amnesia. Anterograde amnesia refers to an inability to learn new information and retrieve it later as part of a long-term memory trace (Scoville & Milner, 1957 ). H.M. was unable to learn the names of the hospital staff, even years after his surgery and after repeated exposure to these individuals (Milner, Corkin, & Teuber, 1968 ). He was severely impaired regarding episodic memory, or memory for autobiographical events that are associated with a specific time, place, and emotion (Tulving, 1984 ), and semantic memory, consisting of general knowledge about the world (Tulving & Schacter, 1990 ). He was also unable to learn new vocabulary or apply new meanings to existing words (such as the computer-related meaning for Windows®) (Gabrieli, Cohen, & Corkin, 1988 ). In contrast, retrograde amnesia refers to memory loss extending back in time from the surgery or accident that caused the amnesia (Ribot, 1882 ; Squire, Clark, & Knowlton, 2001 ). For example, H.M. could recall early childhood memories, but not events that happened in the years immediately prior to his surgery.

  Although H.M. was severely impaired on most tests of memory (including, but not limited to, verbal, spatial, and object-base stimuli presented in visual and auditory domains), he was able to learn some new information (Corkin, 2002 ). He could acquire tasks that tapped skill or habit learning, demonstrating decreased reaction times and increased accuracy on a mirror-tracing task over repeated sessions. Although he could not explicitly recall the task from one session to the next, his performance improved with practice (Milner, 1962

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  Forgetting

  Myths, Perils and Compensations

  • Douwe Draaisma(Author)
  • 2015(Publication Date)
  • Yale University Press

    (Publisher)

  The operation concentrated mainly on the hippocampus, a dual organ that lies in both the left and the right cerebral hemisphere, on the inner side of the temporal lobe. It is shaped rather like a seahorse – hence the name – and is extremely sensitive to electrical stimulation. After the oper-ation the fits were indeed reduced, but the price H.M. had paid soon became clear. Part of his past had been wiped from his memory, but far worse was the fact that he was no longer able to form new memories, a type of memory loss known as ‘anterograde amnesia’. Tragic though this was for H.M., the story goes on, it represented an important step forward for neuropsychology. Alzheimer’s disease and Korsakoff ’s syndrome also cause memory loss, but they affect the brain as in memory of henry m. 59 a whole and do not allow us to draw any conclusions about the location of specific memory processes. Trauma caused from the outside, such as a bullet wound, cannot impact upon areas deep within the brain without damaging those closer to the surface. Because of H.M. it was now clear that the hippocampus, much of which had been removed on both sides, is essential for the storing away of new memories. It emerged that memories do not reside in the hippocampus itself, because H.M. still had access to some of his ‘older’ memories. The fact that he could retrieve them indi-cates that the reproduction of memories relies on different neuronal mechanisms from the storing of them. For many years, H.M. was the purest case of anterograde amnesia known to the medical world. Researchers at MIT regularly brought him to their lab to take part in experiments, which provided a series of new insights into the neuronal representation of memory processes. Everyone described Henry as friendly and cooperative, and he was always more than willing to participate in experiments or to have his damaged brain scanned using yet another new imaging technique.

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  Handbook of Episodic Memory

  • Ekrem Dere, Alexander Easton, Lynn Nadel, Joseph P Huston, Joe P Huston(Authors)
  • 2008(Publication Date)
  • Elsevier Science

    (Publisher)

  Subsequently, animal models of human memory impairment identified the anatomical structures within the medial temporal lobe that are important for understanding H.M.'s memory impairment: the hippocampal region (hippocampus proper, dentate gyrus, and subicular complex) and the perirhinal, entorhinal, and parahippocampal cortices (Squire and Zola-Morgan, 1991 ; Lavenex and Amaral, 2000). Testing of H.M. over many years consistently found intact intellectual and perceptual functions (Milner et al., 1968 ; Corkin, 1984). These observations gave support to the idea that the capacity for forming new memories is a distinct cerebral function, separable from other perceptual and cognitive functions. Recently, this idea has been reexamined. A group of seven memory-impaired patients with damage to the medial temporal lobe was found to be impaired on tests of visual-perceptual abilities that involved difficult-to-discriminate stimuli (Lee et al., 2005a, b). This new work raised the possibility that suitable tests of memory-impaired patients might reveal perceptual deficits that were not detected by more conventional tests (Lee et al., 2005c). We have addressed this issue by studying six memory-impaired patients with well-characterized lesions (Bayley et al., 2005 ; Gold and Squire, 2005). Two of these patients (E.P. and G.P.) are severely amnesic and have large lesions of the medial temporal lobe bilaterally due to herpes simplex encephalitis. Both patients have extensive, virtually complete, bilateral damage to the hippocampus, amygdala, entorhinal cortex, and perirhinal cortex, as well as approximately 70% of the parahippocampal cortex

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